: Tools have been developed for planning and delivering intensity-modulated conformal radiotherapy (IMCRT), a variant of new x-ray treatment techniques that use a computer-controlled linear accelerator to deliver dose distributions that are significantly superior to those that can be delivered using procedures currently practiced in radiation oncology. Before IMCRT can be implemented on a routine basis, additional tools are needed to verify the computer-controlled treatment delivery, refinements are needed on tools that have been developed to verify patient positioning, and protocols for IMCRT need to be demonstrated in a working system. The specific aims for this work are: (1). To develop dose distribution verification tools for IMCRT. A digital instrument will be developed to rapidly and accurately measure the dose distribution delivered by the IMCRT procedure before it is administered to the patient for whom the procedure was planned. Images produced by the instrument will provide the radiation oncologist the assurance that the high dose distribution will be delivered at the prescribed location, and that the reduction in dose planned for normal tissues structures will be delivered at the planned locations. A Monte Carlo simulation will be developed to verify dose distributions calculated by inverse planning before implementing them clinically. (2) To implement image-based patient position verification. Techniques will be implemented and refined that will verify that the target and normal anatomical structures within the patient are positioned daily at the locations planned to receive the prescribed doses. Images of the patient in treatment position on the accelerator will be acquired using the high-energy treatment beams. The differences between the intended and actual positions will be measured from the images to allow for corrective repositioning between or prior to treatments. (3) To demonstrate the implementation of IMCRT. A fully-functional IMCRT implementation will be demonstrated using commercially available equipment. Small pilot studies will be designed to show that complications are eliminated or significantly delayed using IMCRT. The achievement of these aims will form the basis for wide-spread use of IMCRT. The procedure developed here will be available for use in inter-institutional protocols to systematically investigate IMCRT as a means to reduce toxicity and improve local control through dose escalation.